Method and system for controlling automotive hvac apparatus

ABSTRACT

A system and method for automatically controlling the operation of a climate control system, such as a HVAC, in a vehicle. The system disclosed here includes a monitoring module coupled to a blower motor and a controller coupled to the monitoring module and a compressor. The monitoring module monitors the status of the blower motor, and provides the status condition to the controller. Subsequently, the controller transmits an operational command to the compressor based on the inputs received from the monitoring module.

BACKGROUND

This application relates generally to the field of climate control systems in vehicles, and more particularly to controlling the operation of such systems.

Heating, Ventilation, and Air Conditioning (HVAC) systems, also known as climate control systems, regulate a vehicle's internal temperature, humidity, and airflow, ensuring those parameters remain as desired by the passengers. HVAC systems commonly employ a blower motor to receive either ambient or re-circulated air, which is then directed into the interior cabin of the vehicle through ducts. Depending on the configuration of the HVAC system, a passenger may directly control the system by setting the temperature and flow rate of the circulated air, or a system may provide for indirect control, with the passenger selecting a desired cabin temperature.

Vehicles operate in a variety of environments, and thus debris such as twigs and leaves can enter and possibly obstruct the blower motor or its fan. An obstructed blower motor cannot deliver air at the flow rates expected by the control system, and therefore the system will most likely fail to achieve the desired levels of passenger comfort. Alternatively, manufacturing faults, circuit disconnects, or other known factors may the blower motor to malfunction. A system compressor would react to a failed blower motor by operating with very low compressor inlet refrigerant pressure, in turn producing low oil circulation. Moreover, in hybrid vehicles, employing electronic compressors, a failed blower may result in high compressor revolutions per minute (rpm). These conditions can reduce compressor life significantly. Plainly, improved operation would result if a non-operational blower would shut down the compressor to avoid damage.

Conventionally, a low side pressure switch may be employed to turn off the compressor, in case of low suction pressure. The low side pressure switch, however, cycles between “on” and “off” states, which may not be efficient. Thus, this switch may still impose the risk of damaging the compressor.

It would be highly desirable to have an efficient system for vehicles, which automatically detects a blower motor fault, ensuring compressor durability.

SUMMARY

One embodiment of the present application describes a system for controlling the operation of a climate control system, such as a HVAC, in a vehicle. The system includes a monitoring module coupled to a blower motor and a controller coupled to the monitoring module and a compressor. The monitoring module monitors the status of the blower motor, and provides the status condition to the controller. Subsequently, the controller transmits an operational command to the compressor based on the inputs received from the monitoring module. The operational commands may include a normal operation or a turn off command.

Another embodiment of the present application discloses a method for controlling a climate control system in a vehicle. The method includes monitoring the output signal received from a blower motor to identify an undesirable condition, and subsequently, setting the operational status of a compressor. If the undesirable condition is not detected, the method includes transmitting a normal operation command to the compressor and the compressor operates as desired. If however, the undesirable condition is detected at the monitoring step, the method transmits a turn off command to the compressor, and consequently, turns off the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described below set out and illustrate a number of exemplary embodiments of the disclosure. Throughout the drawings, like reference numerals refer to identical or functionally similar elements. The drawings are illustrative in nature and are not drawn to scale.

FIG. 1 is an exemplary embodiment of an HVAC system of the present disclosure.

FIG. 2 outlines a flow chart of an exemplary embodiment of a method for controlling the operation of the HVAC system described in FIG. 1.

DETAILED DESCRIPTION

The following detailed description is made with reference to the figures. Exemplary embodiments are described to illustrate the subject matter of the disclosure, not to limit its scope, which is defined by the appended claims.

Overview

In general, the present disclosure describes a method and system for controlling a climate control system in a vehicle, with the goal of protecting the system compressor. The climate control, or HVAC, system described in this disclosure refers to systems generally employed in various types of vehicles including small or large cars, trucks, vans, SUVs, and trailers. Typically, HVAC systems employ a blower and compressor working in tandem. If the compressor operates with a faulty blower, however, compressor damage could well result. The present disclosure describes a mechanism for actively monitoring the blower motor to identify undesirable conditions posing risk to the compressor, and subsequently turning off the compressor as a precautionary measure. As the term signifies, an undesirable condition is one that may detrimentally affect the compressor To this end, conditions indicating a nonfunctioning blower, such as a non-operational blower motor, a fused motor, zero current output, circuit disconnects, or substantially low voltage drop, are detected. This capability, rendered by the present disclosure, provides durability features to a vehicle HVAC system.

Exemplary Embodiments

FIG. 1 illustrates an exemplary HVAC system 100 for supplying conditioned air to a passenger compartment of a vehicle. Among other devices, the HVAC system 100 includes a blower or fan (not shown) having a blower motor 102, which is operatively coupled to a blower motor relay 104, and a compressor 106. A control head 108 provides an interface by which a user selects a desired operating mode. Based on the chosen settings, the control head 108 sends operational commands to the coupled HVAC system components, such as the compressor 106 and the blower motor 102 (through the blower motor relay 104). For example, a desired temperature setting selected by the user at the control head 108 is provided to the blower motor 102 through the blower motor relay 104. The blower motor relay 104 receives input power from a power supply +VBAT 109. The compressor 106 may be a mechanical or electric compressor known to those skilled in the art. Those skilled in the art will appreciate that a conventional HVAC system includes other components such as a condenser, a thermal expansion valve, and so on; for description purposes, however, those components do not affect the present disclosure, and such components are not discussed here, in the interest of clarity and simplicity.

The HVAC system 100 employs a conventional control head such as the control head 108 for operating in different desired modes. Those skilled in the art will appreciate that the control head 108 may include a set of controls, including a blower speed control, a temperature control, an air outlet control, and so on, each of which may be manipulated by the user for selection from the different modes of operation. For example, the temperature control may be switched between hot and cold modes. The control head 108 may accept user inputs through input devices such as a touch screen, buttons, or other known interface elements. In addition, the control head 108 is coupled to a power train control module 110. Selection or manipulation of a control, such as changing the temperature control to “colder” or inputting a desired cabin temperature, causes a corresponding signal generation by the power train control module 110. As shown, the signal received from the control head 108 is interpreted and passed on to the compressor 106 by the power train control module 110 through a relay 112. Alternatively, a transistor, a CAN signal, or other known devices may be employed to pass signal from the power train control module 110 to the compressor 106.

The system 100 also includes a variable blower control (VBC) 114 (shown by dotted line) capable of controlling the operating speed of the blower motor 102. The VBC 114, having any suitable processor 115, may be in electrical communication with the blower motor 102 via electrical ports 116 and 118, which correspond to the positive and negative input, respectively, of the blower motor 102. As shown, the VBC 114 may include other connections such as a ground connection 128, or a (pulse width modulation) PWM input 122 from the control head 108. In general, the VBC 114 receives a blower speed value at the PWM input 122 from the control head 108, and subsequently the VBC 114 changes the revolution speed of the blower motor 102. Alternatively, the VBC 114 may receive a DC voltage, and this DC voltage may be converted to a corresponding PWM signal. Blower controllers such as the VBC 114 are well known to those skilled in the art and will not be discussed in detail in the present disclosure. In addition, Alternate control modules such as an Electronic Automatic Temperature Control (EATC), a Remote Climate Control Module (RCCM), a Dual Automatic Temperature Control (DATC), may also be employed to monitor the blower motor 102.

As discussed, the blower motor 102 and the compressor 106 operate in tandem, and failure of the blower motor 102 may detrimentally affect the compressor 106. Such a situation may result in substantially low suction pressure and low percentage oil in circulation, imposing a risk of damage to the compressor 106. Blower motor malfunctioning leads to undesirable conditions for the compressor 106. The signal received from the blower motor 102 may be monitored to measure the voltage drop, current output, or revolution speed which may indicate the undesirable condition. For example, substantially low voltage drop, zero current or substantially low current, substantially high current, disconnected blower motor, or substantially low rotational speed are some of the undesirable conditions. Those skilled in the art will appreciate that known measuring techniques may be employed to measure voltage drop across the blower motor, and current output. In addition, fluctuations in voltage or current may be used to identify motor rpm. One such process of identifying the undesirable condition via current measurement is described in detail in the following sections. Typically, blower malfunctioning may arise due to various known reasons including, but not limited to, stalled motor, locked rotor, fused motor, or electrical disconnections. It should be evident that blower malfunctioning requires shutting down the compressor 106 as a precaution against damage.

The present disclosure turns off the compressor 106 upon detection of an undesirable condition. To this end, the VBC 114 measures parameters associated with the blower motor 102 such as voltage drop, current output, revolution speed, or other known parameters that identify inappropriate functioning of the blower motor 102. For example, zero current output, together with voltage at the blower motor 102, indicates that the blower motor 102 is not working, and serves as a detection mechanism for an undesirable condition. If one or more undesirable conditions are detected, the VBC 114 provides this information to the control head 108 through a feedback line 124.

On receiving the undesirable condition indication through the feedback line 124, the control head 108 provides this information to the power train control module 110, which in turn switches off the compressor 106. In addition, no signal on the feedback line may also indicate an undesirable condition, which may result in turning off the blower motor 102 as well as the compressor 106. In general, based on the operating mode selected by a user, the power train control module 110 transmits normal operation commands to the compressor 106. Detection of an undesirable condition by the VBC 114, however, results in termination of the normal operation commands and instead, the power train control module 110 sends a turn off command, which switches off the compressor 106.

An exemplary technique to detect an undesirable condition through the current measurement is set out here. The embodiment of the present disclosure employs a shunt resistor 126 within the VBC 114, as shown by the dotted line. The shunt resistor 126 is connected between an electrical connection 120 to the electrical ground 128 to monitor the current of the blower motor 102. To this end, the VBC 114 measures the voltage drop across the shunt resistor 126 using the electrical connect 120 and the ground line 128, and compares this voltage drop with the PWM signal received from the control head 108. Typically, the PWM signal specifying the desired blower speed should substantially correlate to the operating speed. A threshold value for the blower current may be predetermined to identify an undesirable condition. For a desired operating speed, a current value below a lower limit may be considered undesirable as the blower motor 102 may not be rotating substantially. The VBC 114 informs the control head 108 of this condition, and consequently, the control head 108 transmits a signal corresponding to turn off command to the compressor 106. In another case, the current value above an upper limit may indicate a stalled motor or a locked rotor in the motor, requiring blower and compressor turn off. It should be evident to those skilled in the art that alternate controllers, sensors, or gauging devices may be employed to measure and detect failure of the blower motor 102.

As the VBC 114 actively monitors the blower motor 102 to identify the undesirable conditions, the present disclosure provides automatic control of the compressor 106 requiring no manual intervention. In one implementation, after turning off the compressor 106 to protect its durability, the system 100 may inform or alert the driver of blower issue through an interface such as the control head 108, or other known vehicle information display interfaces.

FIG. 2 illustrates a method 200 for controlling an HVAC system such as the HVAC system 100 shown in FIG. 1. The method 200 discussed in the following sections may be applicable to any climate control system employed in a vehicle where the malfunctioning of the blower detrimentally affects compressor operation.

The method 200 begins at step 202, where the VBC 114 monitors the output signal received from the blower motor 102. The monitoring step involves measuring the output current or voltage drop across the blower motor 102 to detect inappropriate functioning of the blower motor 102, creating an undesirable condition for the compressor 106. Alternatively, the frequency of rotation (rpm) of the blower motor 102 may also be measured.

Based on the signal monitored at step 202, the VBC 114 identifies whether the blower motor 102 is creating an undesirable condition for the compressor 106 at step 204. The undesirable condition may be blower motor conditions that may detrimentally affect the compressor 106; the undesirable condition may be, but is not limited to, significantly low blower motor voltage drop, zero current draw, or frequency of rotation below a threshold value.

In case at least one undesirable condition is detected, the method 200 proceeds to step 206, where a turn off command is transmitted to the compressor 106. In an embodiment of the present disclosure, on detecting the undesirable condition, the VBC 114 informs the control head 108 of this condition, and the control head 108 in turn sends the turn off command using the power train control module 110. Subsequently, the compressor 106 is turned off.

In case no undesirable condition is detected at step 204, the method 200 includes transmitting normal operation command to the compressor 106 at step 208. Normal operational operation command are typical commands sent to the compressor 106 under different modes of operations and are known to those skilled in the art. In addition, the method 200 goes back to step 202 to continuously monitor the output of the blower motor 102 to detect an undesirable condition. The method 200 continues until an undesirable condition is detected, and as a result, the compressor 106 is turned off until the blower starts operating appropriately again.

The specification has set out a number of specific exemplary embodiments, but those skilled in the art will understand that variations in these embodiments will naturally occur in the course of embodying the subject matter of the disclosure in specific implementations and environments. It will further be understood that such variation and others as well, fall within the scope of the disclosure. Neither those possible variations nor the specific examples set above are set out to limit the scope of the disclosure. Rather, the scope of claimed invention is defined solely by the claims set out below. 

1. A system for controlling the operation of a climate control system in a vehicle, the system comprising: a monitoring module, coupled to a blower motor, configured to monitor the status of the blower motor; and a controller operatively coupled to the monitoring module and a compressor, configured to: receive inputs from the monitoring module; and transmit an operational command to the compressor based on the inputs received from the monitoring module.
 2. The system of claim 1, wherein the operational command includes: normal operation; or turn off.
 3. The system of claim 2, wherein the controller sends the normal operation command to the compressor on detection that the blower motor is operational.
 4. The system of claim 2, wherein the controller sends the turn off command to the compressor on detection of an undesirable condition.
 5. The system of claim 4, wherein the undesirable condition is detected using one or more blower motor parameters including: current; voltage; or revolutions per minutes.
 6. The system of claim 4, wherein the undesirable condition is identified when the controller receives no input from the monitoring module.
 7. The system of claim 4, wherein the monitoring module is configured to continuously measure the output signal received from the blower motor to detect the undesirable condition.
 8. The system of claim 1, wherein the climate control system is a heating, ventilation, and air conditioning (HVAC) system.
 9. A system for controlling a compressor of a climate control system in a vehicle, the system comprising: a monitoring module, coupled to a blower motor, configured to monitor the status of the blower motor to detect an undesirable condition; and a controller operatively coupled to the monitoring module and a compressor, the controller configured to: receive inputs from the monitoring module; and transmit a turn off command to the compressor on detection of the undesirable condition.
 10. The system of claim 9, wherein the controller transmits normal operation command to the compressor until the detection of the undesirable condition.
 11. The system of claim 9, wherein the climate control system is a heating, ventilation, and air conditioning (HVAC) system.
 12. The system of claim 9, wherein the undesirable condition is detected using one or more blower motor parameters including: current; voltage; or revolutions per minutes.
 13. The system of claim 9, wherein the undesirable condition is identified when the controller receives no input from the monitoring module.
 14. A method for controlling the operation of a climate control system in a vehicle, the method comprising: monitoring the output signal of a blower motor to identify an undesirable condition; and setting the operational status of a compressor including: transmitting a normal operation command to the compressor upon a determination that no undesirable condition identified; or transmitting a turn off command to the compressor upon a determination that the undesirable condition is identified. 